Process for the production of nitriles

ABSTRACT

IMPROVEMENT IN THE PRODUCTION OF NITRILES BY HEATING CARBOXYLIC ACIDS OR THEIR FUNCTIONAL DERIVATIVES WITH UREA, WHICH IMPROVEMENT CONSISTS IN THE ADDITIONAL USE OF AMIDOSULPHONIC ACID IN THE REACTION MIXTURE.

United States Patent 3,646,103 PROCESS FGR THE PRODUCTION OF NITRILES Juergen Luecke, Tubingen, Germany, assignor t Sandoz Ltd.

No Drawing. Continuation-impart of application Ser. No. 807,914, Mar. 17, 1969. This application Jan. 15, 1970, Ser. No. 3,217

Int. Cl. C07c 121/00, 121/02, 121/12 US. Cl. 260-465 13 Claims ABSTRACT OF THE DISCLOSURE Improvement in the production of nitriles by heating carboxylic acids or their functional derivatives with urea, which improvement consists in the additional use of amidosulphonic acid in the reaction mixture.

The present application is a continuation-in-part application of my application Ser. No. 807,914, filed Mar. 17, 1969.

It is known to produce nitriles by reacting a mixture of a carboxylic acid or a functional derivative of a carboxylic acid and urea at a temperature superior to 250 C. It has been found that this reaction can be effected at lower temperatures and in shorter times when amidosulphonic acid (H NSO H) is added to the reaction mixture.

Carboxylic acids which can be converted into the corresponding nitriles by the aforementioned process include, e.g., the aliphatic carboxylic acids, in particular saturated aliphatic monocarboxylic acids having 2 to 10 carbon atoms, e.g. acetic, propionic, butyric, hexanecarboxylic and octanecarboxylic acids; the cycloaliphatic carboxylic acids, e.g. cyclohexanemonocarboxylic acid; especially suitable are mononuclear and binuolear aromatic monocarboxylic and dicarboxylic acids, e.g. benzenecarboxylic, naphthalene-l-carboxylic, naphthalene 2 car-boxylic, diphenyl-2-, -3- and -4-carboxylic, isophthalic, terephthalic and diphenyl-Z,2'-dicarboxylic acid; and heterocyclic acids, e.g. monocarboxylic acids of heterocyclic 5- or 6- membered ring systems which may bear in particular nitrogen, oxygen or sulphur as hetero atoms, e.g. thiophene- 2- and -3-carboxylic acid and nicotinic acid. These acids may bear carbon substituents, e.g. halogen, in particular chlorine or bromine, as in chloroacetic, 2-chloropropionic and 2-, 3- and 4-i'luoro, -chloro-, -bromoand -iodo-benzenecarboxylic acids; alkyl groups, as in Z-methyl-butyric, 2-methyl-3-ethyl-pentanecarboxylic, 2-, 3- and 4-methylbenzenecarboxylic acids, the methylnaphthalenecarboxylic acids, quinaldinecarboxylic acid and S-methylnicotinic acid; aralkyl radicals, as in 5-benzylnicotinic acid, aryl radicals; e.g. phenyl radicals, as in phenylacetic, benzothiophene-2-carboxylic, benzthiophene-3-carboxylic and 5-phenylthiophene-2-carboxylic acids; nitro groups, as in 2-, 3 and 4-nitrobenzoic acids; heterocyclic radicals, in particular mononuclear 5- or 6-membered rings containing nitrogen, oxygen or sulphur hetero atoms, as present in thiophene-Z-acetic acid; acyl groups, as in brombenzophenone-carboxylic acids; and cyano, mercapto, tertiary amino, alkyloxy, ether, ester and organic sulphonyl groups. The reaction is of course applicable only with carboxylic acids that are stable at the reaction temperature, which excludes those acids that are decarboxylated at the reaction temperature.

The salts, in particular the alkali metal salts and the earth alkali metal salts, of these carboxylic acids are particularly suitable functional derivatives, e.g. the sodium salts, the potassium salts, the calcium salts, the ammonium salts; further the anhydrides and halides, e.g. the chlorides, and in the aromatic series the corresponding trihalogenomethyl compounds. Examples of functional acid derivatives are ammonium-Z-chlorbenzoate, acetic anhydride, 4-nitrobenzoyl chloride and 1-methyl-4-trichloromethylbenzene. As noted above, the functional derivatives other than the trihalogenomethyl compounds are non-oxo-carbonylic derivatives of a corresponding carboxylic acid.

It is of special advantage to employ the amidosulphonic acid in amounts ranging from about 1 mole to 2.5 moles or more, particularly 1.5 to 2 moles, per one equivalent of the carboxyl group or carboxylic derivative, while the optimum amounts of urea range from about 0.5 to 2 moles or more, particularly 1 to 1.5 moles.

Instead of being added as such, the amidosulphonic acid can, if preferred, be formed in the reaction mixture, for example by adding sulphuric acid and the extra amount of urea required for formation of the acid. The formation of amidosulphonic acid by reaction of urea and sulphuric acid is described, for example, in Helvetica Chimica Acta 29, 1438 (1946).

The reaction yielding the nitrile can be conducted in the presence or in the absence of an inert reaction medi um. Thus carboxylic acid, amidosulphonic acid and urea can be dissolved or suspended in an inert organic compound of high boiling point, e.g. benzophenone, which is liquid under the reaction conditions, or they can be melted in mixture with each other without the use of an inert medium. The reaction mixture is maintained at the appropriate temperature until the reaction is complete, which generally takes about 30 to 60 minutes at temperatures between and 240 C. or, optimally, at 220- 240 C.

On completion of the reaction the nitrile is isolated in the usual way and, if desired, purified. It can be purified by distilling off the other substances present in the mixture, or by extraction with an organic solvent of low boiling point, e.g. a chlorinated aliphatic hydrocarbon, in particular chloroform, trichlorethylene, perchlorethylene, cyclohexane or benzene, with subsequent distillation. Sometimes the impurities can be extracted with water.

In the following examples the parts are by weight and the temperatures in degrees centigrade.

EXAMPLE 1 A mixture of 60 parts of glacial acetic acid, 194 parts of amidosulphonic acid and 60 parts of urea is maintained for one hour at 220 230 with reflux. The acetonitrile thus [formed is distilled 01f after this time.

In place of 60 parts of glacial acetic acid, 51 parts of acetic anhydride can be used with equally good results.

Thiophene-Z-carboxylic acid nitrile can be produced in the same way starting from 128 parts of thiophene-Z-carboxylic acid, and similarly pyridine-3carboxylic acid nitrile from 143 parts of pyridine-3-carboxylic acid.

EXAMPLE 2 31.4 parts of 2-chlorobenzoic acid, 36 parts of amidosulphonic acid and 16.8 parts of urea are mixed in a vessel equipped with an air-cooled condenser and the mixture is reacted for 1 hour at an inner temperature of 220-230. The 2 chlorobenzonitrile thus formed is distilled off under normal or reduced pressure and, if desired, is crystallized from petroleum ether.

In place of 2-chlorobenzoic acid, an equivalent amount of one of its alkali metal or ammonium salts or the anhydride of the acid can be employed with equally good success.

This procedure can be employed further for the production of naphthalene-l-carboxylic acid nitrile from naphthalene l-carboxylic acid, of naphthalene-Z-carboxylic acid nitrile from naphthalene-Z-carboxylic acid, of Z-fluorobenzonitrile from 2-fiuorobenzoic acid, and of phenylacetonitrile from phenylacetic acid.

3 EXAMPLE 3 A mixture of 196 parts of benzotrichloride, 194 parts of amidosulphonic acid and 80 parts of urea is reacted for one hour at 240 with reflux. The resulting benzonitrile is distilled ofi, shaken with a saturated potassium carbonate solution, dried and distilled again.

EXAMPLE 4 A mixture of 167 parts of isophthalic acid, 194 parts of amido-sulphonic acid and 120 parts of urea is maintained for one hour at 240. On cooling the reaction mixture is shaken with chloroform and filtered. After removal of the chloroform by distillation, isophthalic acid nitrile is obtained.

Terephthalic acid nitrile is obtained when terephthalic acid is employed in place of isophthalic acid.

This same procedure is employable with equivalent amounts of other acids to yield the following compounds:

2-nitrobenzonitrile from Z-nitrobenzoic acid 3-nitrobenzonitrile from 3-nitrobenzoic acid 2-chloro-S-nitrobenzonitrile from Z-chloro-S-nitrobenzoic acid 3-chlorobenzonitrile from 3-chlorobenzoic acid 4-chlorobenzonitrile from 4-chlorobenzoic acid 2-bromobenzonitrile from 2-bromobenzoic acid 2-iodobenzonitrile from 2-iodobenzoic acid EXAMPLE 5 A mixture of 46 parts of 1-chloro-2-trichloromethylbenzene, 36 parts of amidosulphonic acid and 16.8 parts of urea is reacted for one hour at 220240 interior temperature and with stirring. On cooling, water at 70 is added, after which the mixture is allowed to cool further and then filtered. The product, 2-chlorobenzonitrile, is washed with aqueous ammonia solution, dried and distilled.

Similarly good results are obtained starting from 36 parts of Z-chlorobenzoyl chloride. This route can be employed to obtain 4-nitrobenzonitrile from 33.4 parts of 4 nitrobenzoic acid, for which product recrystallization from alcohol is a convenient method of purification. With parts of nicotinic acid, nicotinic acid nitrile is formed, which is isolated by extraction with chloroform followed by distillaton of the chloroform.

EXAMPLE 6 25.6 parts of cyclohexanecarboxylic acid, 36 parts of amidosulphonic acid and 16.8 parts of urea are mixed and reacted in a vessel with reflux condenser for one hour at 220-230 interior temperature. On cooling the contents of the vessel are extracted several times with warm chloroform. After distilling ofl the chloroform, cyclohexanecarboxylic acid nitrile is obtained which can be purified by distillation.

This procedure can be employed to produce benzonitrile from benzoic acid and 4methyl-benzonitrile from 4- methylbenzoic acid.

EXAMPLE 7 12.3 parts of calcium 2-chlorobenzoate, 12.5 parts of amidosulphonic acid and 6 parts of urea are mixed in a vessel equipped with an air-cooled condenser and the mixture is heated for 1 hour at an inner temperature of 220- 230". The 2-chlorobenzonitrile thus formed is distilled off under normal or reduced pressure. The yield is 54% of theory.

The yields obtained with the operating procedures detailed in the foregoing examples are good to very good, considering the relatively moderate reaction conditions employed. Many nitriles are obtained in yields greater then 75% of theory and a good number, including bromoand iodobenzonitrile, in yields equal to about 90% of theory.

Having thus disclosed the invention what I claim is:

1. In producing a nitrile by heating to reaction temperature a reaction mixture comprising urea and a functional derivative of a carboxylic acid corresponding to the nitrile and selected from the group consisting of an aliphatic carboxylic acid, a cycloaliphatic carboxylic acid, a carbocyclic mononuclear aromatic carboxylic acid and a carbocyclic binuclear aromatic carboxylic acid, the functional derivative being stable at the reaction temperature and being a non-oxo-carbonylic derivative corresponding to the carboxylic acid, the improvement wherein at least about one mole of amidosulphonic acid, per equivalent of carboxyl group in said carboxylic acid, is in the reaction mixture, the amount of urea in said reaction mixture being at least about 0.5 mole per equivalent of carboxyl group in said carboxylic acid.

2. A process according to claim 1 wherein the functional derivative is an alkali metal salt.

3. A process according to claim 2 wherein the alkali metal is sodium.

4. A process according to claim 1 wherein the functional derivative is an alkaline earth metal salt.

5. A process according to claim 3 wherein the salt is calcium 2-chlorobenzoate and nitrile is 2-chlorobenzonitrile.

6. A process according to claim 1 wherein the functional derivative is an ammonium salt.

7. A process according to claim 1 wherein the functional derivative is an anhydride.

8. A process according to claim 7 wherein the anhydride is acetic anhydride and the nitrile is acetonitrile.

9. A process according to claim 1 wherein the functional derivative is an acid halide.

10. In producing a nitrile by heating to reaction temperature a reaction mixture comprising urea and a functional derivative of a carboxylic acid corresponding to the nitrile and selected from the group consisting of a carbocyclic mononuclear aromatic carboxylic acid and a carbocyclic binuclear aromatic carboxylic acid, the functional derivative being stable at the reaction temperature, the improvement wherein at least about one mole of amidosulphonic acid, per equivalent of carboxyl group in said carboxylic acid, is in the reaction mixture, the amount of urea in said reaction mixture being at least about 0.5 mole per equivalent of carboxyl group in said carboxylic acid and said functional derivative being a carbocyclic trihalomethyl aromatic corresponding to the carboxylic acid.

' 11. A process according to claim 10 wherein the trihalomethyl aromatic is benzotrichloride and the nitrile is benzonitrile.

12. A process according to claim 1 wherein the reaction temperature is within the range from to 240 C.

13. A process according to claim 12 wherein the reaction temperature is within the range from 220 to 240 C.

References Cited UNITED STATES PATENTS 2,322,914 6/1943 Biggs 260-4652. 2,339,672 l/l944 Biggs 260465.2 2,444,828 7/1948 Kaplan 260465.2 X 2,783,264- 2/1957 Klapproth, Ir. 260-4652 X 2,800,496 7/1957 Toland, Jr 260-465.2 X 2,824,118 2/1958 Frank et a1. 260465.2 3,131,209 4/1964 King 260465 OTHER REFERENCES Kirsanov et al., C. A. 44, 1950 (pp. 6384-6385).

JOSEPH P. BRUST, Primary Examiner US. Cl. X.R.

*zgz g UNITED STATES PATENT or CE CERTIFICATE OF COEC'HON Patent No. ,646,103 Dated February 29, 1972 lnventor(s) Juergen Luecke It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, beneath line 7, insert Claim priority, application Switzerland, March 27, 1968, 4559/68 line 52, "acid," should read v acid; line 53, "radicals; ....e.g.." should read radicals, e g. Column 2, line 10, '"carboxylic" should read carboxyl Column 4, claim 5, line 2, "and nitrile" should read and the nitrile Signed and sealed this 27th day of February 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

